The invention relates to a ventilation system for head and neck surgery used under a surgical drape so as to prevent the patient from rebreathing carbon dioxide. Excessive amounts of CO.sub.2 in the blood leads to a condition known as hypercapnia. This is a universal problem with all draped head or neck surgeries performed under a local anesthetic. In patients who develop hypercapnia, significant medical problems can arise, such as elevated blood pressure, an increased sensitivity of the heart that can lead to arrhythmia, acute anxiety, claustrophobia, and disorientation.
Providing a surgical drape with support apparatus around the head, along with the provision of pressurized oxygen, is shown in U.S. Pat. Nos. 4,223,669 (Morledge) and 3,482,571 (Behrendt), both of which elevate the surgical drape above the patient's face. Additional U.S. Pat. Nos. 4,377,161 (Whitt) and 4,739,753 (Brehm) also teach surgical drape supports and oxygen breathing apparatus approximate the patient's face. In none of the patents previously mentioned is there a venturi action by the use of a high velocity jet within a conduit utilized to draw in additional outside air which is mixed with the high velocity jet and supplied in the area of the patient's face. Also, none of the above mentioned references teach a positioning bracket for the air supply conduit which is bendably positioned around the chest area of the patient as done in the present invention.
Another method commonly used to supply oxygen to patients under a drape is the utilization of a cannula which is inserted directly into the nasal passageway of the patient and provides a pressurized oxygen source directly into the patient's nasal passage. The cannula method does not provide a passage of a breeze of air over the patient's face which not only diminishes the CO.sub.2 levels but also inhibits the claustrophobic feeling a patient sometimes has with a drape in contact with their face.
The general principle of utilizing a high pressure jet in a duct to draw in and pump surrounding stationary air is generally disclosed in U.S. Pat. No. 4,274,406 (Bartholomew) which is a tracheotomy mask. The high velocity jet in this mask configuration is offset from the axis of the inlet duct since it passes through the wall of the duct and the jet is not positioned along the axis of the duct for optimum performance.
U.S. Pat. No. 4,495,946 (Lemer) is a similar venturi action jet utilized for artificial respiration of a patient which is intermittently valved open and closed. The high speed jet in this patent is likewise offset from the center axis of the duct.